Method of mining relatively thick mineral deposits



Sept. 8, 1970 c, R, THOMPSON 3,527,500

METHOD OF MINING RELATIVELY THICK MINERAL DEPOSITS Filed Feb. 2'7, 1969 3 Sheets-Sheet l INVENTORI CULLEN R. THOMPSON 8Y2 HIS ATTORNEY Sept. 8, 1970 c. R. THOMPSON 3,527,500

METHOD OF MINING HELATIVELY THICK MINERAL DEPOSITS 3 Sheets-Sheet 2 Filed Feb. 27, 1969 INVENTOR:

CULLEN R. THOMPSON HIS AT TORNEY Sept. 8, 1970 c, R M N 3,527,500

METHOD OF MINING RELATIVELY THICK MINERAL DEPOSITS Filed Feb. 27, 1969 3 Sheets-Sheet 5 INVENTORI CULLEN R. THOMPSON HIS ATTORNEY United States Patent 3,527,500 METHOD OF MINING RELATIV ELY THICK MINERAL DEPOSITS Cullen R. Thompson, Denver, Colo., assignor to Shell Oil Company, New York, N .Y., a corporation of Delaware Filed Feb. 27, 1969, Ser. No. 802,835 Int. Cl. E21c 41/04 US. Cl. 299-11 Claims ABSTRACT OF THE DISCLOSURE A method of mining a relatively thick subterranean mineral deposit by extending a borehole into the deposit through the roof and floor thereof. The borehole within the deposit is enlarged and tapered pillar roof and floor support forms are formed extending outwardly from the enlarged borehole to the roof and floor, respectively, of the deposit. The enlarged borehole, including the tapered pillar roof and floor'support forms, is then filled with solidifying material and mineral is mined from the deposit.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to mineral mining; and, more particularly, to a method for mining mineral from a relatively thick subterranean deposit.

Description of the prior art There are many methods known for mining ore and other mineral resources from subterranean deposits, as for example tunneling and the room and pillar methods. However, such methods may be relatively expensive and, in the case of deposits such as coal, may not be at all competitive in view of the availability of other types of fuels. Relatively thick subterranean coal seams, for example, may not "be mechanically exploitable by known room and pillar methods. Further, in such methods, coal, ore, etc., normally found in the deposits, may have to be left behind in substantial amounts for support, otherwise undesired caving and possible surface subsidence may take place. Such materials may comprise up to fifty percent of the material in place.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method for economically exploiting relatively thick subterranean mineral deposits.

It is a further object of this invention to provide a method for accelerating the mining of subterranean deposits.

These objects are preferably carried out by extending a borehole into a subterranean deposit through the roof and into the floor thereof. The borehole is enlarged within the deposit and tapered pillar roof and floor support forms are formed extending outwardly from the enlarged borehole to the roof and floor, respectively, of the deposit. The enlarged borehole or pillar, including the tapered pillar roof and floor support forms, is filled with solidifying material and the mineral is mined from the deposit.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view of a borehole extending into a subterranean mineral deposit in accordance with the teachings of my invention.

FIG. 2 is a vertical sectional view of the enlarged borehole of FIG. 1 with tapered roof and floor supports formed therein;

FIG. 3 is a vertical sectional view of the enlarged borehole of FIG. 2 with solidifying material being injected therein;

Patented Sept. 8, 1970 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, FIG. 1 shows a borehole 11 extending through a subterranean earth 12 into communication with a relatively thick mineral deposit 13. Borehole 11 passes through the roof 14 of deposit 13 and preferably extends at least a short distance below the floor 15 thereof. When used throughout this specification, the word roof refers to the hanging wall of metal mining operations and the ceiling of any underground excavation. The word floor includes the foot wall of metal mining operations.

Referring now to FIG. 2, borehole 11 is reamed so as to form a pillar 11a with tapered roof and floor supports 16 and 17, respectively. This may be accomplished by conventional means, such as by hydraulically washing out borehole 11 until support forms 16 and 17 and pillar 11a are formed. Such washing-out means might include jetting out undesired material by use of hydraulic jetting tools, as for example the jetting tools manufactured by Dowell Schlumberger Corporation of Tulsa, Okla., described on page 1562 of the Composite Catalog of Oil Field Equipment and Services, World Oil, 1968-69 edition. The desired configuration for pillar 11a, roof and floor support forms .16 and 17 may be determined by any known means, such as conventional acoustical or caliper surveys.

Referring now to FIG. 3, a tubing string 18 is preferably disposed in well borehole 11. Tubing string 18 is preferably coupled at one end to a source (not shown) of solidifying material, as for example a cement aggregate, and the material is emplaced throughout the enlarged cavity.

Referring now to FIG. 4, the solidifying material is allowed to set (i.e., solidify) in the pillar 11a and roof and floor support forms 16 and 17 by preferably maintaining a moderate pressure on the cement aggregate until it sets.

If desired, reinforcing steel may be emplaced in the cement aggregate before it sets as illustrated in FIG. 5 wherein like numerals refer to like parts of FIG. 4. Thus, reinforcing rods 19, such as structural steel rods, may be disposed, preferably vertically extending throughout the extent of pillar 11A to above the roof and below the floor supprt forms 16 and 17, respectively, as illustrated in FIG. 5.

The mineral may then be exploited from deposit 13 by any means known in the art, as for example conventional room and pillar methods or modifications thereof. For example, mineral may first be mined from deposit 13 adjacent to the roof 14. The roof is then roof-bolted by means of placing bolts 20 in roof 14 by conventional roof-bolting techniques. Conventional strain gauge equipment may then be installed in the mined-out area of deposit 13 to provide maximum control and safety during the total time the entire deposit .13 is being mined out by selectively lower and lower cuts. After the first cut adjacent the roof 14, portable safety cage equipment may be used in all Working areas as is well known in the mining art.

Although various steps have been described above for extending borehole 11 into deposit 13 with subsequent forming of a cement aggregate therein, it may be possible to core hole evaluate deposit 13 and place support pillars therein in one operation. Further, the techniques of my invention may be applied to any mining operation which would use pillars for roof support, such as in coal mining.

In addition, the material jetted (i.e., removed) from the deposit can be recovered, whereas if conventional room and pillar methods are used, the mineral left behind for necessary support could not be produced, resulting in waste of natural resources. Such emplacement of supports in accordance with my invention prior to actual mining operations could accelerate mineral production and simplify exploitation. Certain conventional oil field techniques, known in the art, may be used to place such support forms as described in detail hereinabove.

The cavity profiles of pillar 11a, roof support form 16 and floor support form 17 may be determined by conventional means as discussed herein-above. For example, sonar tools may be used to survey the underground cavity. One such technique is discussed in an article appearing in the Sept. 16, 1968 issue of the Oil and Gas Journal, pp. 76 through 78, entitled, Sonar Tool Surveys Underground Cavities by Ernest Nolte.

I claim as my invention: 1. A method of mining a relatively thick mineral deposit having a roof and floor disposed in a subterranean earth, said method comprising the steps of:

extending a borehole from the surface of the earth through the roof of said deposit into the floor thereof;

enlarging said borehole within said deposit and forming tapered pillar roof and floor support forms extending outwardly from said enlarged borehole to the deposit roof and floor, respectively;

filling said enlarged borehole including said tapered pillar roof and floor support forms with a solidifying material;

mining mineral adjacent to the roof of said deposit;

bolting said roof; and

subsequently proceeding down said deposit mining mineral from the roof to the floor thereof.

2. The method of claim 1, wherein the step of forming tapered pillar roof and floor support forms includes the steps of:

enlarging the borehole within the deposit and undercutting from said enlarged borehole a short distance below said roof outwardly and upwardly to said roof, thereby forming said tapered roof support form; and undercutting from said borehole a short distance above said floor outwardly and downwardly to said floor thereby forming said tapered floor support form.

3. The method of claim 1 including the step of positioning reinforcing means in said enlarged borehole prior to filling said borehole with a solidifying material.

4. The method of claim 3 wherein the step of positioning reinforcing means in said borehole includes the step of:

placing reinfOrcing rods throughout the'extent of said enlarged borehole to points above said roof and below said floor.

5. The method of claim 1 wherein the step of filling said borehole includes the steps of:

placing a cement aggregate in said borehole; and

maintaining pressure on said cement aggregate until i said cement aggregate solidifies.

References Cited UNITED STATES PATENTS 1,751,607 3/1930 Smith 6l53.6

FOREIGN PATENTS 834,975 3/1952 Germany. 779,401 7/ 1957 Great Britain.

ERNEST R. PURSER, Primary Examiner US. Cl. X.R. 61--45, 53.6 

